Im biting my tounge, because I did kinda give a 30 min away when I got tutored with my homework, so technically I guess that wasn't totally free, more of a trade.
Anyway, I would print it and the person would keep it after they bought it. I woulds sign code words on each one in my writing so if there was one with a code word I didn't know, then I would know it was a fake. There would also be a secret something thats different on each coupon and only I would know what to look for
The expiration dates would move. Like the front ones would be like the first one or 2 months and the next for the months after that and so on. I would also list which ones had been used for the person so they dont make copies. And yes, you will initial after delivery